The present invention relates to vinylphenylpropionic acid derivatives, a production process therefore, a polymer thereof and a radiation sensitive resin composition. More specifically, it relates to vinylphenylpropionic acid derivatives preferably having an acid decomposable substituent, a production process therefore, a polymer thereof and a radiation sensitive resin composition which comprises the polymer and is useful for lithography using radiation such as far ultraviolet radiation typically from a KrF excimer laser or ArF excimer laser, charged corpuscular beams such as electron beams or X-radiation such as synchrotron radiation.
In the field of lithography typically used for the production of integrated circuit elements, the design rule of lithography has been decreasing to obtain higher integration. The development of a lithography process which enables a pattern as fine as 0.5 xcexcm or less to be formed stably has been under way vigorously. As a result, a lithography process using radiation having a short wavelength (wavelength of 300 nm or less) which is effective in increasing the range of Depth of Focus (DOF) as well as in reducing the design rule has been developed.
Examples of such radiation having a short wavelength include far ultraviolet radiation from a KrF excimer laser (wavelength of 248 nm) or ArF excimer laser (wavelength of 193 nm), X-radiation such as synchrotron radiation and charged corpuscular beams such as electron beams. As a high-resolution resist for use with the above radiation having a short wavelength, International Business Machine (IBM) Corporation has proposed a xe2x80x9cchemically amplified resistxe2x80x9d and the improvement of this chemically amplified resist is now under way energetically.
The chemically amplified resists are divided into a positive type and a negative type. A positive type chemically amplified resist basically comprises a substance which generates an acid upon exposure to radiation (to be referred to as xe2x80x9cradiation sensitive acid generating agentxe2x80x9d hereinafter) and a resin which is protected by an acid dissociable group, is insoluble or hardly soluble in an alkali and becomes alkali-soluble when the acid dissociable group is dissociated (to be referred to as xe2x80x9cacid dissociable group-containing resinxe2x80x9d hereinafter). A resist pattern is formed, making use of a phenomenon that when the resist film is exposed to radiation (to be referred to as xe2x80x9cexposurexe2x80x9d hereinafter), the radiation sensitive acid generating agent generates an acid, the decomposition reaction of the acid dissociable group is carried out in the resist film by the catalytic function of this acid, and an exposed portion becomes soluble in a developer.
The acid dissociable group-containing resin is obtained by substituting the acidic functional group of a resin containing at least one acidic functional group such as a phenolic hydroxyl group or carboxyl group by at least one acid dissociable group which can be dissociated in the presence of an acid and the resin itself is insoluble or hardly soluble in an alkali. As the acid dissociable group-containing resin having a carboxyl group is generally known a copolymer of acrylic acid or methacrylic acid protected by a t-butyl group or tetrahydropyranyl (THP) group and another monomer. However, a resin containing an acrylic acid or methacrylic acid unit protected by a t-butyl group or THP has low resistance to dry etching and therefore can be used in combination with only a unit having high resistance to dry etching. Then, if there are acid dissociable group-containing monomers having high resistance to dry etching, for example, aliphatic carboxylic acid derivatives having an acid decomposable substituent and substituted by a vinylphenyl group, the resin can be copolymerized with a larger number of monomers, which would be useful for the optimization of a resist resin structure.
Heretofore, the synthesis of a vinylphenylpropionic acid from 4-(2xe2x80x2-chloroethyl)styrene as a starting raw material has been reported (T. Ishizone, et. al, Macromolecules, 1999, 32, 1453-1462, S. Watanabe, et. al, Macromol. Chem. 1992, 193, 2781-2792). However, as this synthesis process is a reaction between a Grignard reagent and carbonic dioxide, it is not suitable for inexpensive and safe industrial-scale production. Further, 4-(2xe2x80x2-chloroethyl)styrene which is a synthesis raw material is not an inexpensive industrial raw material and cannot be easily produced.
As a problem special to this chemically amplified resist, its resist pattern is changed in line width or T-shaped by fluctuations in post-exposure delay (to be referred to as xe2x80x9cPEDxe2x80x9d hereinafter) which is a time from exposure to a heat treatment. In recent years, there have been proposed various chemically amplified resists which can be used for the production of semiconductor devices, including a radiation sensitive resin composition which comprises a polymer consisting of a hydroxystyrene-based recurring unit, a t-butyl (meth)acrylate recurring unit and a recurring unit for reducing the solubility in an alkali developer of the polymer after exposure (JP-A 7-209868) (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d).
However, along with a recent tendency to reduce the design rule of a semiconductor device, the radiation absorption of a resin which is the main ingredient of a radiation sensitive resin composition used cannot be ignored in a chemically amplified resist in order to increase sensitivity while maintaining the rectangularity of a pattern. It has been difficult to use a conventional chemically amplified resist for the production of a semiconductor device having a fine pattern which is expected to be required from now on.
In view of the above situation of the prior art, it is an object of the present invention to provide vinylphenylpropionic acid derivatives which may have an acid decomposable substituent.
It is another object of the present invention to provide an industrially advantageous process for producing the vinylphenylpropionic acid derivatives of the present invention.
It is still another object of the present invention to provide a polymer which has extremely low absorption of radiation and is particularly useful as a resin component of a radiation sensitive resin composition suitable for use as a chemically amplified resist.
It is a further object of the present invention to provide a radiation sensitive resin composition which contains the above polymer, can reduce the difference of effective exposure amount between an upper portion and a lower portion of a resist film, can ensure the rectangularity of even a fine pattern, and is useful as a chemically amplified resist having high sensitivity to various types of radiation such as far ultraviolet radiation from an excimer laser, charged corpuscular beams such as electron beams or X-radiation such as synchrotron radiation (small amount of exposure energy).
It is a still further object of the present invention to provide a radiation sensitive resin composition which is free from a change in the line width of a pattern made therefrom and the T-shaped, deformation of the pattern caused by fluctuations in PED and has excellent resolution.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention are attained by vinylphenylpropionic acid derivatives represented by the following formula (1): 
wherein R1 is a hydrogen atom or a methyl group, R2 and R3 may be the same or different and each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted or a phenyl group which may be substituted, and Z1 is a group represented by the following formula (2): 
wherein R4, R5 and R6 may be the same or different and each a hydrogen atom, an alkyl; group having 1 to 8 carbon atoms which may be substituted or a phenyl group which may be substituted, or any two of R4, R5 and R6may be bonded together with a carbon atom bonded thereto to form a cyclic aliphatic group, or a group represented by the following formula (3): 
wherein R7, R8 and R9 may be the same or different and each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted or a phenyl group which may be substituted, or any two of R7, R8 and R9 may be bonded together with a carbon atom bonded thereto to form a cyclic aliphatic group.
Secondly, the above objects and advantages of the present invention are attained by a process for producing vinylphenylpropionic acid derivatives represented by the above formula (1), comprising the steps of:
(i) reacting an acetate represented by the following formula (4-1): 
wherein R3 is as defined in the above formula (1), Z2 is a group represented by the following formula (2xe2x80x2): 
wherein R10, R11 and R12 may be the same or different and each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted or a phenyl group which may be substituted, or any two of R10, R11 and R12 may be bonded together with a carbon atom bonded thereto to form a cyclic aliphatic group, or a group represented by the above formula (3), and X1 is an eliminating group, with an alkylphosphine represented by the following formula (4-2): 
wherein R13, R14 and R15 may be the same or different and each an alkyl group having 1 to 8 carbon atoms which may be substituted, to form a first quaternary phosphonium salt represented by the following formula (4-3): 
wherein R3 is as defined in the above formula (1), Z2 and X1 are as defined in the above formula (4-1), and R13, R14 and R15 are as defined in the above formula (4-2),
(ii) reacting the formed first quaternary phosphonium salt with a base to form a phosphorus ylide represented by the following formula (4-4): 
wherein R3 is as defined in the above formula (1), Z2 is as defined in the above formula (4-1), and R13, R14 and R15 are as defined in the above formula (4-2),
(iii) reacting the formed phosphorus ylide with a styrene derivative represented by the following formula (4-5): 
wherein R1 and R2 are as defined in the above formula (1), and X2 is an eliminating group, to form a second quaternary phosphonium salt represented by the following formula (4-6): 
wherein R1, R2 and R3 are as defined in the above formula (1), Z2 is as defined in the above formula (4-1) and R13, R14 and R15 are as defined in the above formula (4-2), and
(iv) hydrolyzing the formed quaternary phosphonium salt.
According to the present invention, thirdly, the above objects and advantages of the present invention are attained by a polymer which comprises a recurring unit represented by the following formula (1xe2x80x2): 
wherein R1, R2and Z1 are as defined in the above formula (1), and which as a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) of 1,000 to 500,000.
According to the present invention, finally, the above objects and advantages of the present invention are attained by a radiation sensitive resin composition which contains (A) the above polymer of the present invention and (B) a radiation sensitive acid generating agent.